Postprandial hyperglycemia and postprandial hypertriglyceridemia in type 2 diabetes

Postprandial glucose level is an independent risk factor for cardiovascular disease that exerts effects greater than glucose levels at fasting state, whereas increase in serum triglyceride level, under both fasting and postprandial conditions, contributes to the development of arteriosclerosis. Insulin resistance is a prevailing cause of abnormalities in postabsorptive excursion of blood glucose and postprandial lipid profile. Excess fat deposition renders a vicious cycle of hyperglycemia and hypertriglyceridemia in the postprandial state, and both of which are contributors to atherosclerotic change of vessels especially in patients with type 2 diabetes mellitus. Several therapeutic approaches for ameliorating each of these abnormalities have been attempted, including various antidiabetic agents or new compounds targeting lipid metabolism.

Lipoprotein metabolism in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease （NAFLD）, an pathologies characterized by fatty accumulation in escalating health problem worldwide, covers a spectrum of hepatocytes in early stages, with potential progression to liver inflammation, fibrosis, and failure. A close, yet poorly understood link exists between NAFLD and dyslipidemia, a constellation of abnormalities in plasma lipoproteins including triglyceride-rich very low density lipoproteins. Apolipoproteins are a group of primarily liver-derived proteins found in serum lipoproteins; they not only play an extracellular role in lipid transport between vital organs through circulation, but also play an important intracellu- lar role in hepatic lipoprotein assembly and secretion. The liver functions as the central hub for lipoprotein metab- olism, as it dictates lipoprotein production and to a significant extent modulates lipoprotein clearance. Lipoprotein metabolism is an integral component of hepatocellular lipid homeostasis and is implicated in the pathogenesis, potential diagnosis, and treatment of NAFLD.

Is vitamin D receptor a druggable target for non-alcoholic steatohepatitis?

Nonalcoholic steatohepatitis(NASH)is a progressed stage of non-alcoholic fatty liver disease,and available therapeutic strategies for NASH are limited.Vitamin D receptor(VDR)is proposed as a druggable target for NASH due to the discovery of vitamin D deficiency in NASH patients.To date,vitamin D supplementation has not consistently conferred expected therapeutic benefits,raising the question of whether VDR can serve as a proper drug target for NASH.It is known that VDR can interact with other ligands such as bile acids in addition to vitamin D,and its expression can be induced by fatty acids,and insulin.It has also been shown that while activation of VDR in hepatic macrophages and hepatic stellate cells resulted in attenuation of hepatic inflammation and fibrosis,activation of VDR in hepatocytes could accelerate lipid accumulation.Thus,the multiplicity of VDR ligands,together with the cell type-specificity of VDR activation,must be taken into consideration in assessing the validity of VDR being a potential druggable target for NASH treatment.To this end,we have evaluated the relationship between VDR activation and various contributing factors,such as gut microbiota,bile acid,fatty acids,and insulin,in addition to vitamin D,with an expectation that a potential drug might be identified that can elicit VDR activation in a tissue-and/or cell type-specific manner and therefore achieving therapeutic benefits in NASH.

Insensitivity of PI3K/Akt/GSK3 signaling in peripheral blood mononuclear cells of age-related macular degeneration patients

Our recent studies with cultured retinal pigment epithelium cells suggested that overexpression of interleukin 17 receptor C（IL-17RC）,a phenomenon observed in peripheral blood and chorioretinal tissues with age-related macular degeneration（AMD）,was associated with altered activation of phosphatidylinositide 3-kinase（PI3K）,Akt,and glycogen synthase kinase 3（GSK3）.We wondered whether or not altered PI3 K,Akt,and GSK3 activities could be detected in peripheral blood mononuclear cells（PBMC） obtained from AMD patients.In the patients＇ PBMC,absent or reduced serine-phosphorylation of GSK3α or GSK3β was observed,which was accompanied with increased phosphorylation of GSK3 substrates（e.g.CCAAT enhancer binding protein a,insulin receptor substrate 1,and TAU）,indicative of enhanced GSK3 activation.In addition,decreased protein mass of PI3K85α and tyrosinephosphorylation of PI3K50α was present in PBMC of the AMD patients,suggesting impaired PI3 K activation.Moreover,abnormally lowered molecular weight forms of Akt and GSK3 were detected in PBMC of the AMD patients.These data demonstrate that despite the presence of high levels of IL-17 RC,Wnt-3a and vascular endothelial growth factor,the PI3K/Akt/GSK3 signaling pathway is insensitive to these stimuli in PBMC of the AMD patients.Thus,measurement of PI3K/Akt/GSK3 expression and activity in PBMC may serve as a surrogate biomarker for AMD.

Non-alcoholic fatty liver disease: a narrative review of genetics

Non-alcoholic fatty liver disease(NAFLD) is now the most common cause of chronic liver diseases worldwide. It encompasses a spectrum of disorders ranging from isolated hepatic steatosis to nonalcoholic steatohepatitis(NASH),fibrosis, cirrhosis, and hepatocellular carcinoma. One of the key challenges in NAFLD is identifying which patients will progress. Epidemiological and genetic studies indicate a strong pattern of heritability that may explain some of the variability in NAFLD phenotype and risk of progression. To date, at least three common genetic variants in the PNPLA3, TM6 SF2, and GCKR genes have been robustly linked to NAFLD in the population. The function of these genes revealed novel pathways implicated in both the development and progression of NAFLD. In addition,candidate genes previously implicated in NAFLD pathogenesis have also been identified as determinants or modulators of NAFLD phenotype including genes involved in hepatocellular lipid handling, insulin resistance,inflammation, and fibrogenesis. This article will review the current understanding of the genetics underpinning the development of hepatic steatosis and the progression of NASH. These newly acquired insights may transform our strategy to risk-stratify patients with NAFLD and to identify new potential therapeutic targets.

Re-evaluating the role of epithelial-mesenchymal-transition in cancer progression

Epithelial-mesenchymal transition（EMT） and mesenchymal-epithelial transition（MET） are essential for embryonic development and also important in cancer progression. In a conventional model, epithelial-like cancer cells transit to mesenchymal-like tumor cells with great motility via EMT transcription factors; these mesenchymallike cells migrate through the circulation system, relocate to a suitable site and then convert back to an epithelial-like phenotype to regenerate the tumor. However, recent findings challenge this conventional model and support the existence of a stable hybrid epithelial/mesenchymal（E/M） tumor population. Hybrid E/M tumor cells exhibit both epithelial and mesenchymal properties, possess great metastatic and tumorigenic capacity and are associated with poorer patient prognosis. The hybrid E/M model and associated regulatory networks represent a conceptual change regarding tumor metastasis and organ colonization. It may lead to the development of novel treatment strategies to ultimately stop cancer progression and improve disease-free survival.

Expression of human hepatic lipase negatively impacts apolipoprotein A-Ⅰ production in primary hepatocytes from Lipc-null mice

This study aimed to examine whether expression of human hepatic lipase（hHL） exerted an intracellular effect on hepatic production of apolipoprotein（apo） A-I.The levels of secreted and cell-associated apoA-I were contrasted between primary hepatocytes isolated from Lipc-nuW and C57BL/6 mice,and between Lipc-nuW hepatocytes transfected with either hHL-encoding or control adenovirus.An HSPG-binding deficient hHL protein（hHLmt） was used to determine the impact of cell surface binding on HL action.Accumulation of apoA-I in conditioned media of primary hepatocytes isolated from Lipc-nuW mice was increased as compared to that from C57BL/6 mice.Metabolic labeling experiments showed that secretion of ＇＇S-apoA-I from Lipc-nuW cells was significantly higher than that from C57BL/6 cells.Expression of hHL in Lipc-nuW hepatocytes,through adenovirus-mediated gene transfer,resulted in decreased synthesis and secretion of ＇S-apoA-I,but not S-apoE,as compared with cells transfected with control adenovirus.Expression of HSPG-binding deficient hHLmt in Lipc-nuW cells also exerted an inhibitory effect on apoA-I production,even though hHLmt displayed impaired exit from the endoplasmic reticulum as compared with hHL.Subcellular fractionation revealed that expression of hHL or hHLmt led to increased microsome-association of apoA-I relative to non-transfected control.Expression of hHL negatively impacts hepatic production of apoA-I.

Unraveling complexity of interconnected regulatory circuits in lipid metabolism

In this issue of Journal of Biomedical Research,3review articles are published that cover a broad range of topics addressing current understanding on regulation of nutrient metabolism through protein phosphatases,homeostatic regulation of cellular lipid droplets by small GTPases,and mechanisms by which hepatic assembly and secretion of triglyceride-rich lipoproteins are regulated.

Efficacy of polyphenolic ingredients of Chinese herbs in treating dyslipidemia of metabolic syndromes

There is an increasing interest and popularity of Chinese herbal medicine worldwide, which is accompanied by increasing concerns about its effectiveness and potential toxicity. Several ingredients, such as polyphenolic compounds berberine, flavonoids, and curcumin, have been studied extensively by using various animal models. Effectiveness of treatment and amelioration of metabolic syndromes, including insulin resistance and dyslipidemia, has been demonstrated. This review summarizes the major checkpoints and contributing factors in regulation of exogenous and endogenous lipid metabolism, with particular emphasis centered on triglyceride-rich and cholesterol-rich lipoproteins. Available experimental evidence demonstrating the lipid-lowering effect of berberine, flavonoids and curcumin in cell culture and animal models is compiled, and the strengths and shortcomings of experimental designs in these studies are discussed.